test: improve coverage for json/lex_string.mbt

[rami3l]

Disclaimer: This PR was generated by an LLM agent as part of an experiment.

Summary

coverage of `json/lex_string.mbt`: 76.5% -> 82.4%

[peter-jerry-ye-code-review]

‼️ This code review is generated by a bot. Please verify the content before trusting it.

⚠️ [Potential incorrect error expectation in Unicode escape test]

• Category: Correctness
• Code Snippet:

  test "lex_hex_digits incomplete hex digits" {
    inspect!(@json.parse?("\"\\u123"), content="Err(Unexpected end of file)")
  }

• Recommendation: Verify if the actual error should be about incomplete hex escape rather than EOF
• Reasoning: The test expects EOF error but the root issue is an incomplete Unicode escape sequence (\u123). The lexer might need to throw a specific error about missing hex digits before reporting EOF. For JSON specification, invalid Unicode escapes should produce specific parse errors.

💡 [Test name could be more descriptive]

• Category: Maintainability
• Code Snippet:

  test "lex_hex_digits incomplete hex digits"

• Recommendation: Rename to "lex_unicode_escape with incomplete hex digits"
• Reasoning: The current name doesn't explicitly mention this is testing Unicode escapes. More specific names help developers understand test purpose without reading implementation.

💡 [Missing test case for escaped quote handling]

• Category: Maintainability
• Recommendation: Consider adding a test for \" escape sequence
• Reasoning: While forward slash escape is covered, JSON strings require testing for quote escapes (\"). This is a critical escape sequence that should be explicitly verified to ensure proper string termination handling.

[coveralls]

Pull Request Test Coverage Report for Build 5085

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 85.617%

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Totals
Change from base Build 5083:	0.03%
Covered Lines:	5262
Relevant Lines:	6146

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💛 - Coveralls